In automotive suspension technology it is currently desirable to have the ability to change the height of the body relative to the road depending upon the travel conditions. It is highly desirable to be able to lower the aerodynamic profile of the automobile at high speeds on smooth roads while still being able to raise the sprung portion of the automobile to a much higher level for low speed rough road travel. While it has long been known that the height of the suspension can be adjusted by increasing the pressure in an air adjustable shock absorber in order to increase height such adjustments can only be made manually with the vehicle stopped. In order to continuously make such adjustments, it is necessary for an automatic system to be able to detect the existing height condition of the vehicle and compare it to a standard or to a selected height. Any mechanical systems for measuring the distance between two points of the suspension which are relatively movable to each other as the body is raised and lowered have inherent reliability problems during the long service lives of such suspension members.
It is an object of this invention to develop a low cost infrared height sensor which is small in size and may permit installation within the air suspension system. A further objective is to allow the driver to electronically select among an infinitely variable number of height adjustments while the vehicle is in motion. It is the further object to allow for the replacement of the infrared height sensing device without disassembly of the strut or suspension unit in which it is mounted. A still further object is for the height sensor to be capable of withstanding the environment of the suspension over a temperature range of -40.degree. to 100.degree. C. All objectives are achieved utilizing an infrared height sensing system which is mounted within an air suspension member. The air suspension member remains capable of reliable and consistent control of vehicle height throughout the environmental range of conditions to which automobiles are subjected.